Correlation of the histological distributions and quantitative analyses of physiologically significant regulatory substances and activities in fresh-frozen serial microtome sections of the acid- producing region of the glandular rat stomach would be made to clarify aspects of the mechanisms of acid secretory control in various functional states. These would include feeding and fasting, stimulation of acid secretion by injections of histamine, bethanechol, gastrin pentapeptide, and cortisol and inhibition of the secretion by injections of atropine and prostaglandin E2. The technique and methods to be used were developed largely by the Principal Investigator and coworkers, and have been employed in their previous studies. The components involved in the acid secretory control to be analyzed are constituents of the cyclic AMP system (cAMP, adenyl cyclase that forms it, and phosphodiesterase that destroys it), and the related endogenous histamine-forming system (precursor histidine and histidine decarboxylase-pyridoxal PO4). Limiting factors in each system would be investigated, and interrelations within and between systems would be studied. From the correlated histological localizations and quantitative changes undergone by each of the constituents in relation to acid secretion, the secretory mechanism and its control would be further clarified. The findings could assist us in understanding the derangements in gastric acid secretion associated with pathological processes involving hyper-, hypo-, or achlorhydria--e.g., in gastric ulcer, gastric cancer, and pernicious anemia.